CDK5 regulatory subunit associated protein 3 (CDK5RAP3) is a novel activator of PAK4 and processe... more CDK5 regulatory subunit associated protein 3 (CDK5RAP3) is a novel activator of PAK4 and processes important pro-metastatic function in hepatocarcinogenesis. However, it remains unclear if there are other mechanisms by which CDK5RAP3 promotes HCC metastasis. Here, we showed that in CDK5RAP3 stable knockdown SMMC-7721 HCC cells, p14ARF tumor suppressor was upregulated at protein and mRNA levels, and ectopic expression of CDK5RAP3 was found to repress the transcription of p14ARF. Using chromatin immunoprecipitation assay, we demonstrated that CDK5RAP3 bound to p14ARF promoter in vivo. Furthermore, knockdown of p14ARF in CDK5RAP3 stable knockdown HCC cells reversed the suppression of HCC cell invasiveness mediated by knockdown of CDK5RAP3. Taken together, our findings provide the new evidence that overexpression of CDK5RAP3 promotes HCC metastasis via downregulation of p14ARF.
Poster PresentationExtra centrosomes have long been observed in cancer cells and it has been show... more Poster PresentationExtra centrosomes have long been observed in cancer cells and it has been shown that extra centrosomes are able to mechanistically promote chromosome instability, aneuploidy and cancer invasiveness. However, extra centrosomes without tumourigenesis have been observed in normal polyploid hepatocytes. Polyploidy has been described in the liver for over a century. About 50% of the adult hepatocytes in humans and up to 90% in mice are polyploid naturally. The mechanisms that allow hepatocytes to divide with extra centrosomes and aneuploidy normally or develop hepatocellular carcinoma (HCC) are poorly understood. NIMA-related kinase 2 (NEK2) expression is found to be elevated in tissues of HCC patients and is associated with poor prognosis and drug resistance. NEK2 is a conserved serine / threonine kinase important for centrosome regulation and mitotic spindle formation during cell cycle. It is involved in multiple cellular functions and is able to interact with different binding partners. It regulates centrosome separation by directly phosphorylating the linker components C-NAP1 and ROOTLETIN, which are proteins constituting the basal bodies of specific cell types. Several reports have shown that NEK2 is associated with multiple pathways including Hippo, NFkB and Wnt. Yet, the molecular function of NEK2 in HCC progression remains unknown. Our evidence showed NEK2 mRNA and protein levels were elevated in liver cancer cells. Overexpression of NEK2 promotes HCC cell growth and cell migration. Cell cycle analysis showed an increased content of DNA in NEK2 overexpressing cell lines suggesting NEK2 contribute to aneuploidy in HCC cells. NEK2 overexpression drove early centrosome splitting in a proportion of both HepG2 and SMMC-7721 inducible cell lines. We found that a ROOTLETIN isoform, called TAX1BP2 and which is a putative tumor suppressor in HCC, is a substrate of NEK2. Hence, I am interested to understand the pathogenic roles of NEK2 in cancer, and to develop better therapeutic strategy for HCC
Poster Session 2Centrosome is a major microtubule-organizing centre for regulating spindle assemb... more Poster Session 2Centrosome is a major microtubule-organizing centre for regulating spindle assembly and bipolarity.Evidence suggests that cancer is a multi-step accumulation process of genomic instability resulted from centrosome dysfunction. One of the major forms of genomic instability is chromosomal instability, which is often presented as changes in chromosomal structure and number. Here we show that hepatitis B virus oncoprotein X protein (HBx), a pivotal factor in hepatocarcinogenesis, induces an increase in chromosome number and tumorigenicity. Microscopic observation illustrates that HBx expression results in centrosomal structure abnormality and multiple centrosomes. Molecular mechanism characterization suggests that HBx binds to a centrosome protein called TAX1BP2, which was previously shown to be an intrinsic block of centrosome over-duplication and a tumor suppressor in hepatocarcinogenesis. We further show that HBx down-regulates TAX1BP2 transcription by reducing its promoter activity. Taken together, our findings suggest a mechanism by which HBx results in hepatocarcinogenesis through centrosome dysfunction
Conference Theme: The LKB1-AMPK pathway from basic science to clinical applicationsThe LKB1-AMPK ... more Conference Theme: The LKB1-AMPK pathway from basic science to clinical applicationsThe LKB1-AMPK Meeting: Cancer Cell Signalling Meeting, Marseilles, France, 25-26 June 2010
CDK5 regulatory subunit associated protein 3 (CDK5RAP3) is a novel activator of PAK4 and processe... more CDK5 regulatory subunit associated protein 3 (CDK5RAP3) is a novel activator of PAK4 and processes important pro-metastatic function in hepatocarcinogenesis. However, it remains unclear if there are other mechanisms by which CDK5RAP3 promotes HCC metastasis. Here, we showed that in CDK5RAP3 stable knockdown SMMC-7721 HCC cells, p14ARF tumor suppressor was upregulated at protein and mRNA levels, and ectopic expression of CDK5RAP3 was found to repress the transcription of p14ARF. Using chromatin immunoprecipitation assay, we demonstrated that CDK5RAP3 bound to p14ARF promoter in vivo. Furthermore, knockdown of p14ARF in CDK5RAP3 stable knockdown HCC cells reversed the suppression of HCC cell invasiveness mediated by knockdown of CDK5RAP3. Taken together, our findings provide the new evidence that overexpression of CDK5RAP3 promotes HCC metastasis via downregulation of p14ARF.
Poster PresentationExtra centrosomes have long been observed in cancer cells and it has been show... more Poster PresentationExtra centrosomes have long been observed in cancer cells and it has been shown that extra centrosomes are able to mechanistically promote chromosome instability, aneuploidy and cancer invasiveness. However, extra centrosomes without tumourigenesis have been observed in normal polyploid hepatocytes. Polyploidy has been described in the liver for over a century. About 50% of the adult hepatocytes in humans and up to 90% in mice are polyploid naturally. The mechanisms that allow hepatocytes to divide with extra centrosomes and aneuploidy normally or develop hepatocellular carcinoma (HCC) are poorly understood. NIMA-related kinase 2 (NEK2) expression is found to be elevated in tissues of HCC patients and is associated with poor prognosis and drug resistance. NEK2 is a conserved serine / threonine kinase important for centrosome regulation and mitotic spindle formation during cell cycle. It is involved in multiple cellular functions and is able to interact with different binding partners. It regulates centrosome separation by directly phosphorylating the linker components C-NAP1 and ROOTLETIN, which are proteins constituting the basal bodies of specific cell types. Several reports have shown that NEK2 is associated with multiple pathways including Hippo, NFkB and Wnt. Yet, the molecular function of NEK2 in HCC progression remains unknown. Our evidence showed NEK2 mRNA and protein levels were elevated in liver cancer cells. Overexpression of NEK2 promotes HCC cell growth and cell migration. Cell cycle analysis showed an increased content of DNA in NEK2 overexpressing cell lines suggesting NEK2 contribute to aneuploidy in HCC cells. NEK2 overexpression drove early centrosome splitting in a proportion of both HepG2 and SMMC-7721 inducible cell lines. We found that a ROOTLETIN isoform, called TAX1BP2 and which is a putative tumor suppressor in HCC, is a substrate of NEK2. Hence, I am interested to understand the pathogenic roles of NEK2 in cancer, and to develop better therapeutic strategy for HCC
Poster Session 2Centrosome is a major microtubule-organizing centre for regulating spindle assemb... more Poster Session 2Centrosome is a major microtubule-organizing centre for regulating spindle assembly and bipolarity.Evidence suggests that cancer is a multi-step accumulation process of genomic instability resulted from centrosome dysfunction. One of the major forms of genomic instability is chromosomal instability, which is often presented as changes in chromosomal structure and number. Here we show that hepatitis B virus oncoprotein X protein (HBx), a pivotal factor in hepatocarcinogenesis, induces an increase in chromosome number and tumorigenicity. Microscopic observation illustrates that HBx expression results in centrosomal structure abnormality and multiple centrosomes. Molecular mechanism characterization suggests that HBx binds to a centrosome protein called TAX1BP2, which was previously shown to be an intrinsic block of centrosome over-duplication and a tumor suppressor in hepatocarcinogenesis. We further show that HBx down-regulates TAX1BP2 transcription by reducing its promoter activity. Taken together, our findings suggest a mechanism by which HBx results in hepatocarcinogenesis through centrosome dysfunction
Conference Theme: The LKB1-AMPK pathway from basic science to clinical applicationsThe LKB1-AMPK ... more Conference Theme: The LKB1-AMPK pathway from basic science to clinical applicationsThe LKB1-AMPK Meeting: Cancer Cell Signalling Meeting, Marseilles, France, 25-26 June 2010
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